1. Field of the Invention
The present invention is directed to an atmospheric vaporizer and heat exchanger primarily adapted for vaporizing cryogenic liquids. More particularly, the present invention is directed to an atmospheric vaporizer/heat exchanger which is an assembly of a plurality of finned heat exchange tubes and brackets fixedly attached to one another without the use of self-tapping screws.
2. Brief Description of the Prior Art
Atmospheric vaporizers have been known in the art for a long time. These devices are used in industry to vaporize relatively large quantities of a cryogenic liquid which is needed in the gaseous form for certain manufacturing operations. In essence, an atmospheric vaporizer is a heat exchanger which utilizes ambient heat to vaporize the very low boiling (cryogenic) liquid. A typical example for the use of atmospheric vaporizers/heat exchangers is the vaporization of liquid oxygen for use in various industrial processes and welding operations.
State of the art atmospheric vaporizers/heat exchangers include a plurality of heat exchange elements which are finned tubes made of good heat conducting materials (usually aluminum). The finned tubes are mechanically assembled to one another and to a substantially rigid frame. Flow of the cryogenic fluid through the tubes may be in a parallel (for certain applications) or series fashion, or a combination of the two, to maintain the height of the exchanger within reasonable limits. The relatively large surface of the fins facilitates efficient heat exchange with the environment; in other words, the fins promote relatively efficient absorption of heat from the ambient atmosphere and thus provide the heat required for vaporization of the cryogenic liquid. An atmospheric vaporizer/heat exchanger, including specific dimensions for the fins of its elongated finned tube, is described in U.S. Pat. No. 4,479,359. Further information relating to heat exchangers, and various ways of attaching panels and other items to one another, can be found in the following references: Austrian Patent No. 222310; French Patents Nos. 1,127,107; 1,217,649; 1,027,613; and U.S. Pat. Nos. 4,774,792; 2,307,216; 3,032,603; 3,512,805, and 4,777,777.
State of the art atmospheric vaporizers/heat exchangers typically utilize brackets or plates to interconnect the fins of the finned tubes in order to provide mechanical integrity to the assembled heat exchange tubes. In a typical state-of-the-art assembly, the brackets or plates are attached to the fins with self-tapping screws or by a welding operation. The brackets then are attached to a rigid frame by bolts and nuts positioned through preformed holes in the brackets.
There are significant disadvantages of the above-summarized state-of-the-art assembly. Spacers are required for the assembly of the brackets and finned tubes (or heat exchange elements) while the brackets are fastened to the fins with the self-tapping screws or by welding. Welding is a very labor intensive and therefore a costly operation. Furthermore, the quality of the welds often creates an aesthetic problem. The use of screws to fasten the brackets to the fins is also time consuming. Also, the screws which protrude with their sharp points on one side of the assembled brackets or fins represent a safety hazard. Although the screws used in this operation are typically cadmium plated, the plating is often damaged especially where the screws contact the aluminum fins and brackets, and therefore corrosion is a frequent problem.
The present invention is designed to eliminate or minimize the above-noted problems which have arisen in the prior art with the assembly of the finned heat exchange elements and brackets with screws.